How do I reassemble the key?

Hint 1 of 15:

First, find the key (point B, up the ladder).

Hint 2 of 15:

You also need a ladle (in the kitchen, point H).

Hint 3 of 15:

Now, head to the blacksmith (point C) and get a couple of items there (forge
hammer and hacksaw).

Hint 4 of 15:

In the adjacent room (point D) there is some charcoal you need.